A FORENSIC scientist who has worked on high-profile cases returned to his former school to offer an insight into his job.

Dr Craig Chatterton was asked back to Blackburn’s Queen Elizabeth’s Grammar School, where he studied his A-levels, to give careers advice to students and was quizzed about his work.

Dr Chatterton, who also attended Darwen Vale, told a packed lecture hall about his involvement with the Shannon Matthews case and other high-profile investigations before answering questions.

He told students he had been called in to analyse urine samples and then hair samples in the Shannon case and found evidence of drugs that would cause drowsiness having been ingested by the young girl over a period of time.

Dr Chatterton, 34, said: “Much of my work is involved in analysing biological samples.

“It can be frustrating, even upsetting at times, dealing with some of the cases I have to handle, but you have to forget your personal emotions and remember that you’re a scientist first and foremost.”

After graduating with a Master’s degree in chemistry and a doctorate from Liverpool University, Craig joined the Forensic Science Service nine years ago.

At his base in Euxton near Chorley, he specialises in toxicology – the presence in the body of alcohol, drugs and other substances and their effects on it.

Dr Chatterton said: “When I get called to court, it is as an expert witness. I am there solely to present and answer questions on the scientific facts.”

Head of chemistry at QEGS Alan Sagar, who taught Dr Chatterton and invited him to speak at the school, said: “Craig had proved the importance not only of working hard for his qualifications, but also of developing first-class communication skills.”